scholarly journals Numerical simulation of the effect of flow field in swirl nozzle spinning on yarn performance

2019 ◽  
Vol 70 (06) ◽  
pp. 564-571
Author(s):  
JIANG YAN ◽  
HUA QIU
Keyword(s):  
Numerical Simulation ◽  
Central Area ◽  
Inlet Pressure ◽  
Computational Domain ◽  
Inlet Channel ◽  
Device Structure ◽  
Air Inlet ◽  
The Difference ◽  
Yarn Hairiness ◽  
Yarn Surface

Swirl nozzle spinning is an effective method to reduce ring-spun yarn hairiness due to device structure and vortex characteristics. This study establishes a computational domain of a swirl nozzle comprising an air inlet channel and a yarn channel to investigate the characteristics of the vortex in the swirl nozzle and the effects of inlet pressure on the wrapped force of the yarn. Simulation results show that the airflow rotates clockwise toward the two yarn entrance directions; moreover, the pressure at the central area of the yarn channel is lower than that of the surrounding area, which is good for the yarn’s steady movement and free fibers wrapping on the yarn surface into the yarn body. When the inlet pressure is high, the pressure spreading to each section of the yarn channel is also high. When the difference between the pressure near the inner wall and the yarn axis is high, the yarn surface has added high pressure, and the velocity and its fluctuation are also high. Experiment result reveals that 0.2 MPa is sufficient in significantly reducing yarn hairiness and that operating the nozzle under a low air pressure is economical. Thus, the numerical simulation can provide the theoretical as well as quantitative reference for the vortex tube design in the coming future.

scholarly journals Numerical prediction and experimental analysis of ends-together yarn splicing

2016 ◽  
Vol 87 (12) ◽  
pp. 1457-1468 ◽  
Author(s):  
Akil Osman ◽  
Simon De Meulemeester ◽  
Benny Malengier ◽  
Joris Degroote ◽  
Jan Vierendeels
Keyword(s):  
Flow Field ◽  
Inlet Pressure ◽  
Technical Process ◽  
Inlet Channel ◽  
Predictive Values ◽  
Eddy Simulation ◽  
Velocity Magnitude ◽  
Air Inlet ◽  
Large Eddy ◽  
Insight Into

Pneumatic yarn splicing is a technical process for joining two yarn ends together. The process involves injecting compressed air into a splicing chamber. The inlet pressure and chamber slope determine the main parameters affecting this process. In this paper, large eddy simulation of the flow field in four selected splicing chambers is carried out. The chambers are used for splicing ends-together yarns. The results of these simulations are analyzed to investigate first the effects of the inlet pressure. Secondly, the effects of the geometry of the chambers on the flow field inside the splicing chambers are determined. These effects are studied and analyzed to interpret the experimental results, which have been obtained using the same splicing chambers. This provides further insight into the parameters that are important in order to obtain good splicing characteristics. It is demonstrated that the volume of the splicing chamber and the location of the air inlet channel play crucial roles in the splicing of the end-together yarns. The root mean square values of the velocity magnitude inside a splicing chamber have predictive values for the retained splice strength. The results provide solid evidence on the effectiveness of the computational fluid dynamics technology to study pneumatic splicing and optimize the geometry of an ends-together splicing chamber.

Effect Analysis of Nitrogen Injection on the Variation of “Oxidation Zone” in Coal Mine Gob Based on Numerical Simulation

2016 ◽  
Vol 9 (1) ◽  
pp. 47-54
Author(s):  
Jing Shen ◽  
Mingran Chang
Keyword(s):  
Numerical Simulation ◽  
Coal Mine ◽  
Heat Dissipation ◽  
Spontaneous Combustion ◽  
Oxidation Zone ◽  
Effect Analysis ◽  
Mine Fire ◽  
Nitrogen Injection ◽  
The Difference ◽  
Residual Coal

One of the main reasons for coal mine fire is spontaneous combustion of residual coal in gob. As the difference of compaction degree of coal and rock, the underground gob can be considered as a porous medium and divided into “three zones” in accordance with the criteria. The “three zones” are “heat dissipation zone”, “oxidation zone” and “choking zone”, respectively. Temperature programming experiments are taken and numerical simulation with obtained experimental data is utilized to analyze the distribution of “three zones” in this paper. Different width and depth of “oxidation zone” are obtained when the inlet air velocity is changed. As the nitrogen injection has inhibition effect on spontaneous combustion of residual coal in gob, nitrogen is injected into the gob. The widths of “oxidation zone” are compared before and after nitrogen injection. And ultimately the optimum location and volume of nitrogen injection are found out.

Non-Destructive Measurements of III-V Semiconductor Device Structure by a Hard X-ray Microprobe

1991 ◽  
Vol 240 ◽  
Author(s):  
F. Uchida ◽  
J. Shigeta ◽  
Y. SUZUKI
Keyword(s):  
Semiconductor Device ◽  
Film Structure ◽  
Device Structure ◽  
X Ray ◽  
Model Sample ◽  
Device Structures ◽  
The Difference ◽  
X Ray Absorption ◽  
Non Destructive ◽  
Non Destructive Characterization

ABSTRACTA non-destructive characterization technique featuring a hard X-ray Microprobe is demonstrated for lll-V semiconductor device structures. A GaAs FET with a 2 μm gate length is measured as a model sample of a thin film structure. X-ray scanning microscopic images of the FET are obtained by diffracted X-ray and fluorescence X-ray detection. Diffracted X-ray detection measures the difference in gate material and source or drain material as a gray level difference on the image due to the X-ray absorption ratio. Ni Ka fluorescence detection, on the other hand, provides imaging of 500 Å thick Ni layers, which are contained only in the source and drain metals, through non-destructive observation.

Numerical Simulation Research on the Shape of Top Coal Drawn-Body in Gently Inclined Seam

2012 ◽  
Vol 468-471 ◽  
pp. 2248-2254
Author(s):  
Qiang Li ◽  
Wan Kui Bu ◽  
Hui Xu ◽  
Xiao Bo Song
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Random Medium ◽  
Body Movement ◽  
The Other ◽  
Simulation Research ◽  
Research Results ◽  
Shape Equation ◽  
The Difference ◽  
Meso Scale

The numerical model of top coal drawing in gently inclined seam is built based on PFC2d software. By comparing with the theory of drawn-body movement law, it can be obtained that the shape of top coal drawn-body accords with the theory of random medium movement. The research results show that the form of the shape equation of top coal drawn-body is uniform while the top coal caving angle is different. On the other hand, with the difference of top coal caving angle and drawing height, the shape of top coal drawn-body is differential at the meso scale, which depends on the parameters of the shape equation of top coal drawn-body.

scholarly journals Robust-Output-Controlled Synchronization Strategy for Arrays of Pancreatic β-Cells

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
David I. Rosas Almeida ◽  
Laura O. Orea Leon
Keyword(s):  
Numerical Simulation ◽  
Sliding Mode ◽  
Active Cell ◽  
The Other ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Reference Cell ◽  
The Difference ◽  
Synchronization Scheme ◽  
Second Order Sliding Mode

This paper presents a synchronization strategy based on second-order sliding mode control, to obtain robust controlled synchronization in an array of uncertain pancreatic β-cells. This strategy considers a synchronization scheme with a reference cell, which incorporates the desired dynamics, and an array of cells, which does not demonstrate adequate synchronization. The array may be formed by active and inactive cells having different strengths in gap junctions. For an array with three cells, we design the coupling signal considering that only the output of an active cell of the array is available. The coupling signal is the signum of the difference between the output of the reference cell and the output of an active cell in the array; this ensures exact synchronization in finite time between both cells. Then, this coupling signal is applied to the other cells in the array, and we establish the conditions required to be satisfied to obtain approximate synchronization between the reference cell and all other cells in the array. The performance of this technique is demonstrated by the results of numerical simulations performed for several cases of connections for an array with three cells and the reference cell. Finally, we show through a numerical simulation that this technique can be applied to arrays with many β-cells.

Numerical Simulations of Particle-Laden Flow Based on Given Friction Reynolds Number and Mean Reynolds Number Respectively

2014 ◽  
Author(s):  
Zhenzhong Li ◽  
Jinjia Wei ◽  
Bo Yu
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Wide Spectrum ◽  
Natural World ◽  
Industrial Applications ◽  
Particle Parameters ◽  
The Mean ◽  
The Difference ◽  
Particle Laden Flow

Multiphase flow with particles covers a wide spectrum of flow conditions in natural world and industrial applications. The experiments and the direct numerical simulation have become the most popular means to study the dilute particle-laden flow in the last two decades. In the experimental study, the mean Reynolds number is often adjusted to the value of single-phase flow for each set of particle conditions. However, the friction Reynolds number usually keeps invariable in the direct numerical simulation of the particle-laden flows for convenience. In this study the effect of the difference between given mean Reynolds number and friction Reynolds number was investigated. Two simulations were performed for each set of particle parameters, and the mean Reynolds number and friction Reynolds number were kept invariant respectively. From the results it can be found that the turbulence intensity and the dimensionless velocities are larger when keeping the friction Reynolds constant. And the results calculated from the cases of keeping the mean Reynolds number invariable agree with the experiment results better. In addition, the particle distribution along the wall-normal coordinate was found to be unchanged between two simulation conditions. As a suggestion, keeping the same mean Reynolds number in the direct numerical simulation of particle-laden flow is more appropriate.

Air Characteristics in Air Turbine Spindle of Ultra Precision Machines

2010 ◽  
Vol 297-301 ◽  
pp. 396-401
Author(s):  
Mehrdad Vahdati ◽  
E. Azimi ◽  
Ali Shokuhfar
Keyword(s):  
High Speed ◽  
Design Procedure ◽  
Inlet Pressure ◽  
Cylindrical Shape ◽  
Air Inlet ◽  
Wind Turbine System ◽  
Air Turbine ◽  
Ultra Precision ◽  
The One ◽  
Precision Machines

Air Spindles have been used in ultra precision machines for several years due to their advantages such as high speed rotation, low friction, and low vibration, [1]. Air spindles are widely used in these machines for producing precise work pieces. Although, spindles function on a very complicated theoretical basis, [2, 3], their structure is very simple and consists of mainly a rotor and a stator. The rotor/stator could be made of different shapes. A cylindrical shape is the one commonly in use. The spindle designed in this work has a spherical configuration. It has been designed so that it could be moved without application of electric motor and only by a wind turbine system, [4]. The spindle studied in this research uses compressed air for rotor suspension, and has an air turbine for rotating its shaft. A thin air film acts as bearing layer between rotor and stator. In design procedure, operation parameters such as air inlet pressure for turbine, air inlet pressure for bearing, diameter of turbine nuzzles, diameter of bearing nuzzles, clearance between rotor and stator and etc. have been considered, [5]. A prototype spindle has been manufactured using design criteria. The influence of above mentioned parameters have been recognized through experiments.

Correction of Hot-Wire Measurements in the Near Non-Conducting Wall Region

2000 ◽  
Author(s):  
Li Wenzhong ◽  
B. C. Khoo ◽  
Xu Diao
Keyword(s):  
Numerical Simulation ◽  
Shear Flows ◽  
Control Volume ◽  
Domain Boundary ◽  
Wall Region ◽  
Computational Domain ◽  
Hot Wire ◽  
Conducting Wall ◽  
Simulation Results ◽  
Near Wall

Abstract The present paper is to determine the correction of hot-wire measurements when it is used to measure the shear flows region very close to the non-conducting wall. By numerical simulation of the Navier-Stokes and energy equations using the control volume method, we found that reasonably deployed grid distribution could largely reduce the computational domain size (for a typical Reynolds number for hot-wire near-wall measurements 4.0×10−3∼1.2, the domain boundary placing 650 diameters from the cylinder in front, rear and top is fair enough for accurate simulation, other than the domain boundary which places the 2000 diameters from the cylinder in front and top, and 3000 diameters from the cylinder in rear), and obtain the similar accuracy results for the correction of hot-wire measurements in the near-wall region. Numerical simulation results also show that, only taking the εf,εw (the maximum difference between the respective values of stream function and vorticity on successive iterations) as the criterion for convergence without judge to convergence of the temperature field seems not enough to obtain a convergent simulation result. This may be the possible reason which caused the discrepancy between the simulation results for hot-wire correction when using hot wire to measure the shear flows very close to the non-conducting wall.

Noise reduction of enhanced acoustic balconies on a high-rise building block

2021 ◽  
Vol 263 (1) ◽  
pp. 5327-5334
Author(s):  
SK Tang ◽  
Rudolf YC Lee
Keyword(s):  
Noise Reduction ◽  
Natural Ventilation ◽  
Traffic Noise ◽  
Elevation Angle ◽  
Noise Levels ◽  
Indoor Space ◽  
New Device ◽  
Air Inlet ◽  
The Difference ◽  
The Impact

A new device called 'enhanced acoustic balcony' is installed in a new housing estate in Hong Kong. It is intended to help reduce the impact of traffic noise on the residents. This balcony is basically an enlarged form of a plenum window and with three openings. Apart from the outdoor air inlet, there is the balcony door and a side-hung window on the interior balcony wall for natural ventilation of the indoor space. Sound absorption of NRC 0.7 is installed on the balcony ceiling and its sidewall facing the incoming traffic noise and an inclined panel is installed outside the balcony to provide noise screening. A site measurement of its noise reduction is carried out in the present study in a newly completed housing block. A 28 m long loudspeaker array is used as the sound source. The indoor noise levels are measured according to ISO standard. The results show that the difference between indoor and outdoor noise levels in the presence of this balcony form varies over a relatively narrow range between 10 to 13 dBA for an elevation angle from 25 to 60 deg. There is a weak increase of the noise level difference with elevation angle.

Numerical Simulation and Experiment of Atomization Field of Fan-Shaped Atomization Nozzle for Plant Protection UAV

2021 ◽  
Vol 14 ◽  
Author(s):  
Maohua Xiao ◽  
Yuanfang Zhao ◽  
Zhenmin Sun ◽  
Chaohui Liu ◽  
Tianpeng Zhang
Keyword(s):  
Numerical Simulation ◽  
Size Distribution ◽  
Droplet Size ◽  
Plant Protection ◽  
Cone Angle ◽  
Droplet Size Distribution ◽  
Droplet Velocity ◽  
Inlet Pressure ◽  
Spray Cone Angle ◽  
Spray Cone

Background: There are drift and volatilization of the droplets produced by the plant protection Unmanned Aerial Vehicle (UAV) under the influence of external wind speed and its flight speed. Objective: It studied the atomization characteristics of its fan-shaped atomizing nozzle under different inlet pressures and inner cavity diameters. Methods: For the start, the Realizable k-ε turbulence model, DPM discrete phase model and TAB breakup model are used to make a numerical simulation of the spray process of the nozzle. Then, the SIMPLE algorithm is used to obtain the droplet size distribution diagram of the nozzle atomization field. At last, the related test methods are used to study its atomization performance, and the changes of atomization angle and droplet velocity under different inlet pressures and inner cavity diameters and the distribution of droplet size are discussed. Results: The research results show that under the same inner cavity diameter, as the inlet pressure increases, the spray cone angle of the nozzle and the droplet velocity at the same distance from the nozzle increase. As the distance from the nozzle increases, the droplet velocity decreases gradually, the droplet size distribution moves to the direction of small diameter, and the droplets in the anti-drift droplet size area increase. Under the same inlet pressure, as the diameter of the inner cavity increases, the spray cone angle first increases and then decreases, and the droplet velocity at the same distance from the nozzle increases. As the distance from the nozzle increases, the droplet velocity decreases gradually, the droplet size distribution moves to the direction of large diameter, and the large size droplets increase, which cannot meet the anti-drift volatilization effect. Conclusion: Under the parameter set in this study, when the inlet pressure is 0.6MPa and the inner cavity diameter is 2mm, the atomization result is the best.

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